2018-09-04_GENERAL DOCUMENTS - C1980007

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20 In January 1997, more than 8,000 gpm of water upsurged from the mine floor from a 10-foot cut through a fault area in the first Southeast Headgate off the Box Canyon Mains. Water flooded the mine and some equipment was lost. Water from this inflow was eventually pumped to the surface and discharged to the North Fork of the Gunnison River. Mine water inflow from this area also moved down-dip as the fault was mined through at topographically lower locations. At the end of 1998, the flow was approximately 130 gpm. A significant fault oriented in a S60E direction was encountered by MCC during the initial development of the Sunset Trail Mains in early 2018. No significant inflows of water occurred. The fault is projected to the southeast on Map 9, but has not yet been well characterized. Only minor faulting of limited vertical displacement has been observed in the Blue Ribbon, Bear, and Hawk's Nest Mines. However, in the Bowie #1 Mine, a fault with a displacement of 50 feet was encountered during mining. Drill hole data indicate the presence of other faults in the West Elk Mine life of mine area with similar displacements. One major fault has been encountered in the Elk Creek Mine. The faults which have been encountered in existing mines tend to be high angle, normal faults. Hydrologic Balance - Rules 2.04.5, 2.04.7, 2.05.3(4), 2.05.6(3) and 4.05 Groundwater information can be found in Section 2.04.7 of the PAP. Additional information can be found on Map 34, which shows the location of the groundwater monitoring stations. A description of groundwater occurrence and mining impacts on groundwater within the permit and adjacent areas can be found in the "Probable Hydrologic Consequences of Mining" section of this document and the "Cumulative Hydrologic Impact Study" document for the North Fork of the Gunnison area. There are seven categories of potential aquifers that occur in the Somerset Coal Field. These are: 1) the alluvial and terrace deposits associated with the North Fork of the Gunnison River; 2) the localized, shallow alluvium along creeks tributary to the North Fork; 3) the discontinuous, lenticular and laminar sandstones of the Mesaverde Formation; 4) the Rollins Sandstone; 5) the coal seams; 6) shallow colluvial surficial deposits; and 7) fracture zones in bedrock. Significant hydrogeologic units present within the West Elk Mine permit boundary include (from top to bottom) the Mancos shale, the Mesaverde Formation (including the Rollins Sandstone, Lower Coal Member, Upper Coal Member, and the Barren Member) and the colluvium and alluvium along the drainage side slopes and valley bottoms. These hydrogeologic units are depicted on Map 9 of the PAP. With the exception of the Mancos shale (which has an extremely low permeability and acts as an aquitard), groundwater is generally localized and of limited areal extent within these hydrogeologic units. The Mesaverde Formation is typically 2,500 feet thick at the mine and consists of sandstone, shale, clay, and interbedded coal. Within the members of the Mesaverde Formation, locall y continuous permeable sands may contain groundwater which generally is recharged from the downward percolation of meteoric waters.